1,721,051 research outputs found
Reduction of the cold collisions frequency shift in a multiple velocity fountain: a new proposal
No full textIn this paper, we propose a new scheme for operating an atomic fountain frequency standard. A sequence of time-spaced balls of atoms, launched over nonoverlapping trajectories, makes possible a reduction of the atomic density and consequently the cold collision frequency shift by one order of magnitude without significant reduction of the useful signal and of the overall stability of the clock. The ultimate accuracy of a Cs fountain could be improved below the 10-15 level currently achieved in operating clock
Accurate gas diagnostics for sealed-off CO2 lasers using near-infrared DFB semiconductor lasers
No full textUpdate on Selective Regional Analgesia for Hip Surgery Patients
No full text: In hip surgery, regional anesthesia offers benefits in pain management and recovery. There are a wide range of regional analgesic options; none have shown to be superior. Lumbar plexus block, femoral nerve block, and fascia iliaca block are the most supported by published literature. Other techniques, such as selective obturator and/or lateral femoral cutaneous nerve blocks, represent alternatives. Newer approaches, such as quadratus lumborum block and local infiltration analgesia, require rigorous studies. To realize long-term outcome benefits, postoperative regional analgesia must be tailored to the individual patient and last longer
Blackbody radiation shift of the 133Cs hyperfine transition frequency
No full textWe report the theoretical evaluations of the static scalar polarizability of the 133Cs ground state and of the blackbody radiation shift induced on the transition frequency between the two hyperfine levels with mF=0. This shift is of fundamental importance in the evaluation of the accuracy of the primary frequency standards based on atomic fountains and is employed in the realization of the SI second in the International Atomic Time scale at the level of 1×10−15. Our computed value for the polarizability is α0=(6.600±0.016)×10−39C m2∕V in agreement at the level of 1×10−3 with recent theoretical and experimental values. As regards the blackbody radiation shift we find for the relative hyperfine transition frequency β=(−1.49±0.07)×10−14 at T=300 K in agreement with frequency measurements reported by our group and by Bauch and Schröder [Phys. Rev. Lett. 78, 622 (1997)]. This value is lower by 2×10−15 than that obtained with measurem..
Systematic shift uncertainty evaluation of IEN CSF1 primary frequency standard
No full textWe report a preliminary systematic shift uncertainty evaluation of our cesium fountain and of the first comparison with the NIST-F1 clock of the National Institute of Standard and Technology (NIST) with a two way satellite comparison system. The stability of the time scale UTC (IEN), (generated with a commercial Cs beam) is insufficient to allow evaluation of systematic shifts by conventional techniques; therefore, the accuracy evaluation of the fountain was accomplished using mainly fast differential techniques, resulting in an overall uncertainty of 3/spl times/10/sup -15/
IEN-CsF1 primary frequency standard at INRIM accuracy evaluation and TAI calibrations
No full textAbstract. In this paper we present an accuracy evaluation of the primary frequency standard IEN-CsF1 of the Italian 'Istituto Nazionale di Ricerca Metrologica'. In particular, we discuss the major improvements applied to the frequency standard that have allowed us to reach a total uncertainty of 8 × 10-16 in a measurement period of 20 days to 25 days. The full metrological chain that links the IEN-CsF1 fountain to the International Atomic Time scale is described and characterized, with respect to its noise and performances
Bayesian inference of a negative quantity from positive measurement results
No full textCaesium-fountain frequency standards realize the second in the International System of Units with a relative uncertainty approaching 10(-16). Among the main contributions to the accuracy budget, cold collisions play an important role because of the atomic density shift of the reference atomic transition. This paper describes an application of the Bayesian analysis of the clock frequency to estimate the density shift and describes how the Bayes theorem allows the a priori knowledge of the sign of the collisional coefficient to be rigorously embedded into the analysis. As an application, data from the INRIM caesium fountain are used and the Bayesian and orthodox analyses are compared. The Bayes theorem allows the orthodox uncertainty to be reduced by 28% and demonstrates that it is an important tool in primary frequency metrology
Bayesian estimate of the zero-density frequency of a Cs fountain
No full textCaesium-fountain frequency standards realize the second in the International System of Units with a relative uncertainty approaching 10(-16). Among the main contributions to the accuracy budget, cold collisions play an important role because of the atomic density shift of the reference atomic transition. This paper describes an application of the Bayesian analysis of the clock frequency to estimate the density shift and describes how the Bayes theorem allows the a priori knowledge of the sign of the collisional coefficient to be rigorously embedded into the analysis. As an application, data from the INRIM caesium fountain are used and the Bayesian and orthodox analyses are compared. The Bayes theorem allows the orthodox uncertainty to be reduced by 28% and demonstrates that it is an important tool in primary frequency metrology
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